The present invention relates to control devices and, more particularly, to a bi-directional hall-effect control device.
A control device, as the term is used herein, is a device that produces a desired effect in response to a manual input. In its simplest form, the handle of a tool is a control device. A light switch is slightly more complicated, but nonetheless clearly a control device. In applications where the control device is used frequently, it is desirable that the control device operate consistently and reliably.
In one application, control devices may be used in conjunction with medical ultrasound transducer probes. The users of medical ultrasound transducer probes, hereinafter referred to as sonographers, can obtain images of a region within a body by properly positioning a probe, using a control device such as a handle or knob, against the body. In order to obtain images having diagnostic value, the sonographer may have to physically manipulate the position of the probe by sliding, rotating and tilting the probe.
One area in particular where this manipulation is more challenging is transesophageal cardiac imaging. During transesophageal cardiac imaging, the sonographer positions a transducer housing at the tip of the probe against the esophagus or stomach of a patient to obtain different fields of view of the heart. For transesophageal cardiac imaging, the transducer housing typically contains a number of acoustic transducer elements, which may be sequentially electrically excited by an ultrasound control and operating system to obtain an image in an object plane that is perpendicular to the transducer housing and the transducer elements.
It has been found desirable to provide a control device to rotate the transducer elements contained within the transducer housing independently from the physical manipulation of the housing itself. In combination with the ability to slide, rotate and tilt the transducer housing, the ability to independently rotate the transducer elements within the housing gives the sonographer the ability to obtain an ultrasound image of any or all object planes orthogonal to the upper surface of the transducer elements at each location to which the housing can be moved.
Control devices that allow the sonographer to rotate the transducer elements independently from the transducer housing are known. For example, U.S. Pat. No. 5,402,793 to Gruner et al. shows an ultrasonic transesophageal probe for the imaging and diagnosis of multiple scan planes. The probe includes two buttons that respectively control the clockwise and counter-clockwise rotation of the transducer at the tip of the probe. Each of the buttons is a three-position switch: off, slow rotation and fast rotation. The states of the switches are transmitted to the ultrasound system, interpreted and converted to motor drive signals.
A disadvantage of the Gruner et al. device is that the sonographer is unable to utilize intermediate rotational speeds. A desired position may be overshot when the transducer is rotated in the fast mode, or may take too long to reach when the transducer is rotated in the slow mode. A further disadvantage of the Gruner et al. device is the added complexity, in manufacture and use, of requiring two switches to rotate the transducer. It is desirable to simplify the use and manufacture of the control device. In addition, it is desirable to allow the sonographer to quickly, easily and precisely control the rotational speed of the transducer.
Another known control device is a joystick. For many applications, however, the joystick is simply too large or cumbersome. It is desirable to minimize the size and weight of the control device. It is also desirable to provide a leak proof or hermetic seal around the control device so that the device may be cleaned, disinfected or used in humid environments.
Accordingly, it would be desirable to have an improved control device.